An electrochemical reaction of a fuel cell is an exothermic reaction. To maintain the temperature of the fuel cell at a constant level when generating electric power, a fuel cell system has a cooling apparatus for the fuel cell (refer to, for example, Patent Document 1).
The cooling apparatus has a circulation passage through which a refrigerant is circulated between the fuel cell and a radiator by a pump, a bypass passage for bypassing the radiator, and a thermostat valve for switching between the radiator and the bypass passage when circulating the refrigerant. The thermostat valve performs a switching operation based on the temperature of the refrigerant flowing through the thermostat valve. Further, the cooling apparatus houses the fuel cell, the bypass passage, and the thermostat valve in a single case so as to restrain heat dissipation of the refrigerant when the fuel cell warms up (starts up).
Further, there has also been known a fuel cell system that uses a refrigerant that has passed through a fuel cell as a heat source for air conditioning. For instance, the fuel cell system described in Patent Document 2 is mounted in a fuel cell car, and the exhaust heat of the refrigerant that has passed through the fuel cell is used for heating the interior of the car. The fuel cell system has a cooling line having a radiator and an exhaust heat utilization line having a heater core capable of heat-exchanging the refrigerant with air-conditioning gas, as the lines for circulating the refrigerant to the fuel cell (refrigerant circulation system). If there is a demand for heating the interior of the car, then the refrigerant flows in the cooling line and the exhaust heat utilization line. This causes the refrigerant that has passed through the radiator and the refrigerant that has passed through the heater core to merge and flow into the fuel cell.    [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2004-158279 (Page 4 and FIG. 1)    [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2001-315524 (FIG. 1)